There still exists a need in the art for a method of manufacturing a radiation source. In particular, there still exists a need in the art for a robust, scalable method for manufacturing radiation sources comprising radioactive particles uniformly dispersed in a fixed matrix. Previous methods failed to achieve uniform radiation sources. In particular, there still exists a need in the art for a method of manufacturing a radiation source comprising 191Os. In particular, there still exists a need in the art for a method of manufacturing a radiation source comprising 191Os that is robust and scalable. The present invention answers such needs.